Retortable light excluding container and methods of using same

ABSTRACT

A container includes a gripping groove and a panel structure that allows it to withstand retort or heat sterilization of a low acid liquid nutritional product contained therein. The container can be formed of a multilayer material that has titanium dioxide and iron oxide in an intermediate regrind layer and in at least one of its inner and outer layers. The titanium dioxide and iron oxide are provided together in the same meltable pellets, which are used for forming the container.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 29/175,332 entitled Container and Cap, filed Feb. 3, 2003, which is a continuation-in-part of U.S. patent application Ser. No. 29/175,310 entitled Container, filed on filed Feb. 3, 2003.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to the field of containers, and more particularly to a retortable light excluding plastic container for use with light sensitive low acid liquid nutritional products.

[0003] Low acid liquid food products generally contain nutrients that are light and temperature sensitive. Examples of such liquid foods are nutritional products for infants and nutritious products for persons having specific medical conditions or dietary needs. As used herein and in the claims a “low acid liquid nutritional product” is a liquid nutritional product, other than alcoholic beverages, with a finished equilibrium pH of greater than 4.6. While high acid nutritional products, such as fruit juices and the like, can be cooked and then “hot-filled” into sterile containers in an aseptic filling enclosure; low acid liquid nutritional products must be placed in a sterile container, sealed and then made commercially sterile using a conventional heat and pressure retort process. This post-filling pressurized heat sterilization is often carried out in a batch mode with temperatures in the range of approximately 120-130 degrees Celsius or Centigrade (° C.), which is approximately 248-266 degrees Fahrenheit (° F.). However, prolonged exposure to high temperatures during retort or prolonged exposure to light can result in damage to the biological activity of the nutrients in the product.

[0004] For example, low acid liquid nutritional products typically contain nutrients, including but not limited to vitamins such as vitamin B2 (riboflavin) and vitamin A, that are sensitive to light. Exposure of such food products to light can result not only in damage to the biological activity of these nutrients, but also to the taste or other characteristics of the products. This presents a particular challenge in the packaging of food products, including medical and pediatric nutritional products, because such products are subject to labeling requirements that require that the nutritional contents, e.g., vitamin contents, of the food product be specifically identified. In those cases in which the listed nutritional contents are sensitive to light, there may be a reduction in the amount or activity of one or more of the nutritional contents of the product over time due to light exposure, thereby causing the food product to be out of compliance with its labeling. In such a situation, it may be necessary to reduce the shelf life of the food product, and thus increase the cost of the food product. Alternatively, it may be necessary to increase volume of the nutritional contents of the product, for example, by way of vitamin fortification, which also increases the cost of the food product. It is preferable that a light-protective package be provided so that the nutritional contents of the product remain within the ranges specified in the labeling, thereby providing a longer shelf life for the product.

[0005] Metal cans have conventionally been the preferred means for containing low acid liquid nutritional products in order to provide the needed opaqueness, vitamin protection and hermeticity. However, metal cans are typically not resealable and their weight adds to shipping costs. Metal cans are not resiliently deformable and customers may perceive a dented metal can to indicate a “defective product” that should be returned to the manufacturer, even when the contents are actually unharmed. Some manufacturers have tried relative simple cylindrical-shaped plastic cans, but such cans often distort as a result of the retort process. In addition to the customer perception problem discussed above, permanent plastic container distortion and the resulting shape variances lead to handling problems for the manufacturer during later packaging operations, which are often highly automated.

[0006] U.S. Pat. No. 5,750,226 to Macauley, et al. discloses a bottle designed to provide protection for light-sensitive products contained therein. U.S. Pat. No. 5,750,226 is incorporated herein by reference, in its entirety. Macauley, et al. disclose a bottle having a multi-layered wall structure. The wall includes inner and outer layers of food grade polypropylene, a regrind layer positioned between the inner and outer layers of food grade polypropylene, and a pair of high temperature adhesive layers. The wall further includes oxygen barrier layer. The adhesive layers serve to bond the other layers to the barrier layer. Titanium dioxide (TiO₂) is incorporated into the food grade polypropylene layers and into the regrind layer in order to reduce light transmission through the wall. The titanium dioxide imparts a white color to each layer in which it is present.

[0007] Titanium dioxide is an inert material that can be used in both retort and aseptic packaging techniques. Titanium dioxide is a reflective material, i.e., it works by reflecting light away from the contents of the product. Although titanium dioxide effectively reflects light having a wavelength above approximately 500 nanometers, it has been found that some light having a wavelength below 500 nanometers is reflected when a bottle wall contains relatively high amounts of titanium dioxide. However, as discussed in U.S. Pat. No. 5,750,226, high concentrations of titanium dioxide can create significant problems in the manufacturing of plastic containers. In addition, it can be difficult to achieve high titanium dioxide concentrations in relatively thin container walls.

[0008] Thus, there is a need for an improved plastic container and method for packaging a low acid liquid nutritional product. A primary objective of this invention is to meet that need.

[0009] Another objective of this invention is the provision of a container capable of withstanding heat sterilization in a retort process at temperatures of approximately 120-130° C. (248-266° F.) without significant permanent deformation.

[0010] Another objective of this invention is the provision of a material for enhancing the light excluding properties of a container for low acid liquid nutritional products.

[0011] Another objective of this invention is to reduce the percentage by weight of titanium dioxide required in a container so as to reduce cost, process variability, and wear on tooling, yet maintain or enhance the light excluding characteristics of the container.

[0012] Another objective of this invention is to provide a container that is aesthetically pleasing, as well as easy for automated packaging equipment and consumers to handle.

[0013] These and other objectives will be apparent to one skilled in the art upon studying the drawings, description and claims that follow.

SUMMARY OF THE INVENTION

[0014] The present invention relates to the field of retortable containers in general, and more particularly to a plastic container for use in packaging light sensitive low acid liquid nutritional products.

[0015] A first aspect of the present invention is that the container can be constructed of a light excluding multilayer material that includes an inner layer, an outer layer, and a regrind layer disposed therebetween. The regrind layer and at least one of the inner and outer layers contain titanium dioxide and iron oxide. Optionally, oxygen barrier and adhesive layers can be included if desired.

[0016] A second aspect of the present invention is that container is formed with a side wall and bottom wall configuration that allows it to withstand the retort process. The side wall includes upper, intermediate and lower portions. The upper portion has a convex dome shape, the intermediate portion includes a gripping groove that makes it easier to grasp the container, and the lower portion includes a panel structure defined by a plurality of vertically elongated substantially rectangular indentations separated by a corresponding plurality of longitudinal beams. Optionally, the indentations can include centrally located raised islands therein. The bottom wall can include centrally located primary and secondary recesses that further contribute to the container's capability to withstand the retort process.

[0017] A third aspect of the present invention is the provision of a new method of packaging a low acid liquid nutritional product. The method includes the steps of forming the container as described herein, providing a cap to sealingly mate with the finish of the container, sterilizing the container and cap, filling the container with the low acid liquid nutritional product, hermetically sealing the filled container with the cap, and then heat sterilizing the sealed container in a retort process.

[0018] A fourth aspect of the present invention is the provision of a new method of protecting a light sensitive nutritional product. The method includes the steps of mixing a plurality of meltable color pellets, each containing both titanium dioxide and iron oxide, with a base material, heating the color pellets and the base material, and molding the heated and mixed color pellets and base material to form a layer of a container adapted to hold a light sensitive liquid nutritional product.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a front elevational view of a bottle or container constructed in accordance with the present invention.

[0020]FIG. 2 is a right side elevational view of the container of FIG. 1.

[0021]FIG. 3 is a rear elevational view of the container of FIG. 1.

[0022]FIG. 4 is a top plan view of the container of FIG. 1.

[0023]FIG. 5 is a bottom plan view of the container of FIG. 1.

[0024]FIG. 6 is an enlarged fragmentary cross-sectional view taken along line 6-6 in FIG. 2 and shows a container wall material constructed in accordance with one embodiment of the present invention.

[0025]FIG. 6A is an enlarged fragmentary cross-sectional view similar to FIG. 6 and shows another embodiment of the present invention.

DETAILED DESCRIPTION

[0026] The container or bottle of the present invention is generally designated in the figures by the reference numeral 10. The container 10 is particularly suitable for use in packaging and refrigerated or non-refrigerated storage of medical and pediatric nutritional products such as the products manufactured and sold by Abbott Laboratories through its Ross Products Division. The light barrier characteristics of container 10, as described in detail herein, provided enhanced protection for the nutritional contents, e.g., vitamin contents, of such products. However, it is to be understood that container 10 of the present invention can be used in the packaging (by retort or otherwise) and storage of other light sensitive products without departing from the scope of the present invention.

[0027] The semi-rigid container 10, which is illustrated in FIGS. 1-5, has a hollow body constructed from a multi-layered wall material 12. As best seen in FIG. 6, the wall material has an outer layer 14, an inner layer 16, and a regrind layer 18 disposed between the outer layer 14 and the inner layer 16. In an embodiment of the present invention in which container 10 is constructed to contain a food product, one of ordinary skill in the art will appreciate that outer layer 14 and inner layer 16 can be constructed of plastic, preferably a heat set food grade plastic. More preferably, the layers 14, 16 are preferably constructed of random copolymers containing polypropylene.

[0028] It is preferred, but not required, to construct outer layer 14 and inner layer 16 of the same identical material. Although many food grade plastic materials will suffice, the base or virgin material for the inner and outer layers is most preferably an ethylene-polypropylene random copolymer available from ExxonMobil Chemical Company of Houston, Tex., U.S.A. under the trade designation PP-9122. The ExxonMobil PP-9122 material (hereinafter PP) comes in the form of a plurality of meltable resin pellets, preferably of substantially uniform chemical composition.

[0029] A plurality of meltable resin colorant pellets of substantially uniform chemical composition are mixed, melted, and molded with the virgin PP material to form the outer and/or inner layers 14, 16. The colorant pellets are manufactured by the Ferro Corporation of Independence, Ohio, U.S.A. under the trade designation FERRO CH 010742FLB. The colorant pellets include both titanium dioxide (TiO₂) and iron oxide (FeO₂) in a common pellet, i.e., the same pellet. The titanium dioxide lends a white hue to the colorant pellet and the iron oxide adds a slight amount of black hue, such that overall the colorant pellet has a substantially white or very light grayish hue.

[0030] Thus, outer layer 14 and/or inner layer 16 in the exemplary embodiment of the present invention may contain light barrier additives such as titanium dioxide and iron oxide. The presence of titanium dioxide and iron oxide in outer layer 14 imparts a substantially white color to outer layer 14 that is aesthetically pleasing, thereby making multi-layered material 12 useful in the manufacture of containers for consumer products. Similarly, the presence of titanium dioxide and iron oxide in inner layer 16 imparts a substantially white or grayish color to inner layer 16. When multi-layered material 12 is used in the packaging of food products, it may be desirable to provide a substantially white-colored inner wall in order to provide an aesthetically pleasing appearance to the interior of the package. Thus, when a customer looks into the interior of the package, he/she will see a light grayish inner wall surrounding the product contained in the package. The multilayer material is free of an interlayer of black pigment compound resin disposed between the regrind layer 18 and one of the inner layer 16 and the outer layer 14. This reduces the complexity and cost of the material.

[0031] Of course, the thickness of outer layer 14 and inner layer 16 respectively can vary depending on the packaging needs encountered. However, the U.S. Code of Federal Regulations calls for inner layer 16 to have a minimum thickness of approximately 0.002 inches (0.0508 mm) when container 10 is used to contain a food product. In an exemplary embodiment of the present invention, inner layer 16 has a minimum thickness of approximately 0.002 inches (0.0508 mm), while outer layer 14 has a minimum thickness of approximately 0.002 inches (0.0508 mm).

[0032] Regrind layer 18 can be constructed from a variety of materials. For example, up to approximately sixty percent (60%) by weight of the regrind layer 18 can be constructed from material re-ground from the trim waste of the bottle blow operation used to form the container 10 of this example. The balance of the regrind layer can include virgin PP materials and optionally up to approximately three percent (3%) by weight of EVALCA GF-20, which is used a scrubber, filtering or purifying agent.

[0033] Of course, the regrind layer 18 includes the titanium dioxide and iron oxide colorants contributed by the re-ground material. The colorant pellets described above can also be added to the virgin PP materials added to the regrind, as necessary to maintain the desired equilibrium colorant level in the regrind layer 18. Because the colorant pellet includes both the titanium dioxide and iron oxide colorants in a relatively fixed amount or ratio and only one colorant pellet is used, rather than separate pellets for TiO₂ and FeO₂ respectively, the amount of colorant to add to the regrind layer 18 to achieve the desired steady state equilibrium level is easier to calculate. The mixing process and the resulting color of the inner and outer layers are easier to control because one less factor is variable. One unexpected result is that the total amount of abrasive titanium dioxide used in the container 10 can actually be reduced to less than five percent (5%) by weight, and more preferably to approximately 3.5%.

[0034] Also in this exemplary embodiment, regrind layer 18 has a minimum thickness of approximately 0.007 inches (0.1778 mm). The overall minimum thickness of the container 10 is approximately 0.015 inches (0.381 mm). One of ordinary skill in the art will appreciate that other wall thicknesses are possible without departing from the scope of the present invention.

[0035] Multi-layered wall material 12 may optionally include an oxygen barrier layer 24, as depicted in FIG. 6A. Oxygen barrier layer 24 can be constructed of a variety of materials that are known to provide oxygen barrier characteristics, e.g., ethylene vinyl alcohol (EVOH) and nylons. In one embodiment of the present invention, oxygen barrier layer 24 is constructed of an ethylene vinyl alcohol EVOH copolymer resin. The EVOH resin is preferably EVALCA EVAL LC F101-AZ, available from EVAL Company of America (EVALCA), a subsidiary of Kuraray Co. Ltd. of Japan. The barrier layer preferably has a minimum continuous thickness of approximately 0.0005 inches (0.0127 mm). However, it can be appreciated that the thickness of the oxygen barrier layer 24 may vary without departing from the scope of the present invention. For example, oxygen barrier layer 24 can have a thickness of approximately 0.0002 inches-0.002 inches (0.00508 mm-0.0508 mm).

[0036] In the embodiment shown in FIG. 6A, an inner surface of outer layer 14 is bonded to oxygen barrier layer 24 by way of first adhesive layer 20. An outer surface of regrind layer 18 is bonded to the opposite side of oxygen barrier layer 24 by way of second adhesive layer 22. Thus, oxygen barrier layer 24 is disposed between the outer layer 14 and the regrind layer 18. Placement of the oxygen barrier layer 24 in this position protects layer 24 from moisture that may render it ineffective. In addition, placement of the oxygen barrier layer 24 in this position moves the adhesive layers 20, 22 farther away from the contents of container 10. It will be appreciated that placing the adhesive layers 20, 22 farther away from the contents of container 10 is desirable in those cases in which interaction between the adhesive and the contents may be detrimental to the contents of container 10. One of ordinary skill in the art will recognize that oxygen barrier layer 24 can have other positions relative to inner layer 16, regrind layer 18, and outer layer 14.

[0037] First and second adhesive layers 20, 22 can be constructed of a variety of known adhesive materials known to be useful in bonding materials of the type included in multi-layered wall material 12. For example, first and second adhesive layers 20, 22 can be constructed from polyolefin, e.g., a polyolefin layer having a minimum thickness of approximately 0.0001 inches (0.00254 mm). In the preferred embodiment, the first and second adhesive layers are constructed of MITSUI ADMER QB-520A, available in meltable pellet form from Mitsui Chemicals America, Inc. of Purchase, New York, U.S.A. The minimum values for thickness of the outer, inner, and regrind layers are as stated above and a minimum overall wall thickness for the container 10 of approximately 0.015 inches (0.381 mm) is still preferred in the embodiment illustrated in FIG. 6A. The container 10 of this embodiment has been found to be suitable for containing approximately eight ounces of low acid nutritional product and withstands heat sterilization, up to 130° C. (266° F.), in a conventional retort process without substantial permanent deformation.

[0038] The container 10 of this invention is co-extrusion blow molded in a conventional manner, with the materials for the layers being provided in re-ground or pellet form as described above, mixed, heated and delivered to the appropriate extrusion passages of a multi-station blow wheel molding machine. After molding, the containers are trimmed of excess material or flash and faced to provide the required finish 26 for a hermetic seal by a mating threaded cap or closure. The cap is not shown here but is disclosed in German et al. U.S. Pat. No. 6,276,543, which is incorporated by reference herein.

[0039] The present invention provides a method of packaging a low acid liquid nutritional product that is unique and advantageous over prior methods. The method includes the steps of forming the container 10 with the structural features described below, providing a cap adapted to sealingly mate with the finish of the container, sterilizing the container and the cap, filling the container with a low acid liquid nutritional product, hermetically sealing the open top of the filled container with the cap, and heat sterilizing the sealed container in a retort process. For example, in the case of a container 10 filled with 8 fluid ounces (237 mL) of ENSURE® liquid nutritional product made by the Ross Products Division of Abbott Laboratories, the retort process is carried out as follows. The filled and sealed containers are heated for approximately 13 minutes from ambient room temperature to sterilizing temperature of approximately 126° C. (260° F.). The sterilizing temperature is held for approximately 6 minutes. The peak pressure at the end of the dwell period is approximately 2.48 bar (36 psig). After the dwell, there is a cooling period of approximately 20 minutes. Advantageously the retort process can be carried out at temperature of at least 120° C. (248° F.), more advantageously up to approximately 130° C. (266° F.), and most preferably approximately 126.1 to 127.2° C. (259-262° F.). The method can utilize a single layer material or the multilayer material and the co-extrusion blow molding process described above.

[0040] Referring to FIGS. 1-5, the container 10 of this invention has a bottom wall 28 and a side wall 30, preferably of substantially uniform thickness, joined to the bottom wall 28 to define an open top 32. The side wall 30 has an upper portion 34, an intermediate portion 36, and a lower portion 38. The upper portion 34 has a convex dome shape and terminates at its upper end in a neck and the bottle finish 26. The intermediate portion 36 defines an arcuate annular gripping groove 40 that allows the user to easily grasp the container 10 with the thumb and index or forefinger of one hand. A full radius of approximately 0.3 to 0.5 inches (7.62 mm-12.7 mm), and more preferably approximately 0.328 inches (8.33 mm), defines the gripping groove 40. Most users can comfortably grasp the container 10 by engaging the groove 40 with any one of their other fingers, too. The groove 40 also provides a strong structural hoop for evenly transferring and/or resisting the stresses encountered during the retort process.

[0041] The lower portion 38 has upper and lower ends or end portions 42, 44 respectively that are substantially cylindrical and a panel structure 46 therebetween. The panel structure 46 includes a plurality of vertically elongated, more preferably rectangular, indentations 48 separated by a corresponding plurality of longitudinal beam members 50. Each of the beam members 50 has an arcuate, more preferably circular, lateral cross section that blends smoothly with the substantially cylindrical upper and lower end portions 42, 44. In the preferred embodiment shown, there are six identical opposing indentations 48 separated by six identical opposing beam members 50.

[0042] Each of the indentations 48 has a raised island therein. Preferably the island is centrally located within the perimeter of the indentation 48 and has a substantially rectangular base. The islands 52A, 52B, and 52C have different shapes depending on their location. One pair of opposing islands 52A has identical opposing sides 54A and identical ends 56A that slope inwardly in a four-sided pyramidal manner toward a substantially rectangular flat plateau 58A at the top of the island 52A. One of the opposing islands 52A has a substantially flat recessed area 59, which allows excess flash material left from the ejector pin in the mold to be ground off without adversely impacting the strength or outermost profile of the container 10. Another pair of opposing islands 52B has opposing sides 54B, 54B′ and mirror image ends 56B, 56B′ that slope inwardly toward a substantially rectangular flat plateau 58B. However, side 54B slopes inwardly at a steeper angle than side 54B′. Thus, side 54B′ has a greater surface area than side 54B. Another pair of opposing islands 52C is constructed such that each island 52C is a mirror image of the adjacent island 52B. Thus, the resulting pyramidal structures 52C are skewed in the opposite direction of the islands 52B and have sides 54C, 54C′, ends 56C, 56C′ and a plateau 58C. Each of the indentations 48 includes a sloped planar surface 60 that extends outwardly and downwardly at an acute angle from the bottom of the indentation to join the lower end portion 44.

[0043] As best seen in FIG. 5, the bottom wall 28 of the container 10 also has a configuration that contributes resistance to permanent deformation. The bottom wall configuration is disclosed in U.S. Pat. No. 5,269,437, which is assigned to Abbott Laboratories and incorporated in its entirety by reference herein. In the preferred embodiment, the bottom wall 28 includes a circular or conical primary recess 61 and a substantially flat elliptical secondary recess 62, which are both centrally disposed. The secondary recess 62 has a major axis and a minor axis. The distance across the secondary recess 62 along the major axis divided by the distance across the secondary recess 62 along the minor axis is greater than one but not greater than three. A substantially flat circular annular ring 64 or resting surface surrounds the recesses 61, 62. The bottom wall 28 slopes upwardly and inwardly along the primary recess 61 to join the secondary recess 62 and the ring 64.

[0044] Although the present invention has been described herein with respect to certain exemplary and preferred embodiments, one of ordinary skill in the art will appreciate that various modifications can be made to the multilayer material, the container formed therefrom, and the packaging process without departing from the scope of the invention, which is defined in the appended claims. 

What is claimed is:
 1. A multilayer material comprising: an inner layer; an outer layer; a regrind layer disposed between the inner layer and the outer layer; wherein the regrind layer and at least one of the outer layer and the inner layer contain titanium dioxide and iron oxide.
 2. A multilayer material according to claim 1, wherein the outer layer contains titanium dioxide and iron oxide.
 3. A multilayer material in accordance with claim 1, wherein the inner layer and the outer layer contain titanium dioxide and iron oxide.
 4. A multilayer material in accordance with claim 1, wherein the inner layer comprises an ethylene-polypropylene copolymer.
 5. A multilayer material in accordance with claim 1, wherein the outer layer comprises an ethylene-polypropylene copolymer.
 6. A multilayer material in accordance with claim 1, wherein the inner layer and the outer layer include an identical ethylene-polypropylene copolymer.
 7. A multilayer material in accordance with claim 1, further comprising an oxygen barrier layer, a first adhesive layer, and a second adhesive layer, the first adhesive layer constructed to bond the oxygen barrier layer to an outer surface of the regrind layer and the second adhesive layer constructed to bond the oxygen barrier layer to an inner surface of the outer layer.
 8. A multilayer material in accordance with claim 7, wherein the oxygen barrier layer is constructed from a material comprising ethylene vinyl alcohol.
 9. A container for a light-sensitive product, said container comprising: an inner layer; an outer layer having an inner surface; a regrind layer disposed between said inner layer and said outer layer, said regrind layer having an outer surface; a first adhesive layer disposed adjacent said outer surface of said regrind layer; a second adhesive layer disposed adjacent said inner surface of said outer layer; an oxygen barrier layer disposed between said first adhesive layer and said second adhesive layer, said first and second adhesive layers constructed to bond said oxygen barrier layer to said regrind layer and to said outer layer, respectively; said outer layer containing titanium dioxide and iron oxide; and said regrind layer containing titanium dioxide and iron oxide.
 10. A container according to claim 9, wherein the inner layer contains titanium dioxide and iron oxide.
 11. A container in accordance with claim 9, wherein the titanium dioxide and iron oxide are provided together in common meltable resin pellets and extrusion blow molded to form the retortable container
 12. A multilayer material in accordance with claim 9, wherein the inner layer and the outer layer include an identical ethylene-polypropylene copolymer.
 13. A retortable plastic bottle comprising: a multilayer material that defines a side wall, a bottom wall, and an open top; the multilayer material comprising an inner layer, an outer layer, and a regrind layer disposed between the inner layer and the outer layer, wherein the regrind layer and at least one of the outer layer and the inner layer contain titanium dioxide and iron oxide; the side wall including an upper portion having a convex dome shape and terminating at an upper end in a finish adapted to be hermetically sealed by a cap, a lower portion joined to the bottom wall, and an intermediate portion disposed between the upper portion and the lower portion; the intermediate portion of the side wall defining an arcuate annular gripping groove; and the lower portion being substantially cylindrical at upper and lower ends thereof and including between the substantially cylindrical upper and lower ends a panel structure comprising a plurality of vertically elongated rectangular indentations separated by a corresponding plurality of longitudinal beams members each having an arcuate lateral cross section.
 14. A container in accordance with claim 13, wherein each of the rectangular indentations includes a centrally located raised island that has a vertically elongated generally rectangular base, opposing inwardly sloped side walls, and opposing inwardly sloped end walls.
 15. A container in accordance with claim 13, wherein the gripping groove has a radius of approximately 0.3 inches-0.5 inches (7.62 mm-12.70 mm).
 16. A container in accordance with claim 15, wherein the gripping groove has a radius of approximately 0.328 inches (8.33 mm).
 17. A method of packaging a low acid liquid nutritional product comprising the steps of: forming a container of comprising: a side wall, a bottom wall, and an open top; the side wall including an upper portion having a convex dome shape and terminating at an upper end in a finish adapted to be hermetically sealed by a cap, a lower portion joined to the bottom wall, and an intermediate portion disposed between the upper portion and the lower portion; the intermediate portion of the side wall defining an arcuate annular gripping groove; and the lower portion of the side wall being substantially cylindrical at upper and lower ends thereof and including between the substantially cylindrical upper and lower ends a panel structure comprising a plurality of vertically elongated rectangular indentations separated by a corresponding plurality of longitudinal beams members; providing a cap adapted to sealingly mate with the finish of the container; sterilizing the container and the cap; filling the container with a low acid liquid nutritional product; hermetically sealing the open top of the filled container with the cap; and heat sterilizing the sealed container in a retort process.
 18. A method of packaging a low acid liquid nutritional product in accordance with claim 17, wherein the step of forming the container of comprises co-extrusion blow molding a multilayer material that defines the side wall, the bottom wall, and the open top; the multilayer material comprising an inner layer, an outer layer, and a regrind layer disposed between the inner layer and the outer layer, wherein the regrind layer and at least one of the outer layer and the inner layer contain titanium dioxide and iron oxide.
 19. A method of packaging a low acid nutritional product in accordance with claim 17, wherein the retort process is carried out at temperature of at least 120° C.
 20. A method of packaging a low acid liquid nutritional product in accordance with claim 18, wherein the retort process is carried out at temperature of approximately 126.1 to 127.2° C.
 21. A method of protecting a light sensitive liquid nutritional product comprising the steps of: mixing a plurality of meltable color pellets with a base material, each of the color pellets containing both titanium dioxide and iron oxide; heating the color pellets and the base material; and molding the heated and mixed color pellets and base material to form a layer of a container adapted to hold a light sensitive liquid nutritional product.
 22. A method of protecting a light sensitive liquid nutritional product according to claim 21, wherein the molding step is accomplished by extrusion blow molding and the layer formed is an outer layer of the container. 